For today's typical chassis for motor vehicles, there is a striving that the damper forces for the extension and retraction springing respectively have a relationship in the ratio 2:1 to 4:1. If regulated hydraulic or pneumatic dampers with a characteristic field are utilized for that purpose, then the regulation quality is, however, limited with such a force relationship. Therefore, quickly regulatable vibration dampers are necessary for such regulation circuits.
From the DE 103 20 005 B3, a quickly regulatable vibration damper with adjustable damping force is known, which operates with a magnetorheological fluid. This vibration damper consists of a cylinder in which a piston rod is axially movably guided. This cylinder is surrounded with a further cylindrical housing, in which two throttle paths are arranged, which connect with one another the cylinder chambers that are separated by the piston. A magnetorheological fluid is arranged in the two cylinder chambers, and the viscosity of the magnetorheological fluid is controllable in the area of the throttle paths. For that purpose, field force generating elements are arranged on the throttle paths, and the electrical current supply of the field force generating elements is controlled so that the viscosity of the magnetorheological fluid adjusts itself corresponding to the desired damping. In a particular embodiment of this vibration damper, two independently controllable throttle paths are provided, which make possible a separation of the damping force adjustment dependent on the throughflow direction. Still additionally, non-controllable connection channels are provided in both throttle path inserts, and respectively one non-return check valve for separating the connections channels is arranged in each one of the connection channels. Because the two non-return check valves are oriented contrary to one another and are embodied the same in both throttle paths, the result is that always the same throughflow quantity arises in both throughflow directions, so that also with such a vibration damper the damping regulation of different damper forces for retraction and extension springing or spring travel requires a large regulation spread or range, whereby also in this case the regulation quality is limited.